A single-layer factory-made roofing sheet used on flat roofs — the modern alternative to traditional multi-layer built-up roofing.
A factory-manufactured roofing sheet applied in a single layer, as opposed to the multiple-ply construction of built-up roofing. Single-ply membranes are divided into thermoset (EPDM) and thermoplastic (TPO, PVC) categories. They can be installed ballasted, mechanically attached, or fully adhered and offer advantages in speed of installation and ease of future modification.
On commercial low-slope roofing bids, the single-ply type and attachment method drive both material cost and labor productivity, so an estimator must read the spec carefully before pricing. Substituting one membrane for another, or assuming the wrong attachment, can swing the bid by a large margin and create responsiveness problems if the spec names a particular system. Warranty terms tied to manufacturer-approved installers also affect which subs can be solicited.
Bidding a 60,000-square-foot distribution center, the roofing estimator prices a mechanically attached TPO system per the spec, confirms the GC requires the manufacturer's 20-year NDL warranty, and solicits only certified applicators so the bid holds up at award.
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